Phosphor converted LED with high color quality

Abstract

A light emitting diode (LED) device may include an LED die having a first surface on a substrate. A first phosphor layer may be formed on a second surface and sides of the LED die. The second surface may be opposite the first surface. A second phosphor layer may be formed on the first phosphor layer. The second phosphor layer may have a peak emission wavelength (Lpk2) located between a peak emission wavelength of the LED die (LpkD) and a peak emission wavelength of the first phosphor layer (Lpk2).

What is claimed is: 
     
       1. A light emitting diode (LED) device comprising:
 an LED die configured to emit blue light having a peak emission wavelength; 
 a first phosphor layer disposed on the LED die and configured to emit green, yellow, and red light upon excitation by the blue light emitted from the LED die; and 
 a second phosphor layer disposed on the first phosphor layer opposite from the LED die and comprising a Sr 3 MgSi 2 O 8 :Eu phosphor configured to emit light having a peak emission wavelength at approximately 10 to 50 nanometers longer than the peak emission wavelength of the LED die upon excitation by the blue light emitted from the LED die, the Sr 3 MgSi 2 O 8 :Eu phosphor configured to increase a spectral power distribution (SPD) of the LED device at a local minimum of approximately 470 nanometers as compared with an SPD emission of the LED device without the second phosphor layer, the Sr 3 MgSi 2 O 8 :Eu phosphor configured to produce an x color coordinate of a spectral emission of the LED device that is substantially the same as an x color coordinate of a spectral emission of the LED device without the second phosphor layer. 
 
     
     
       2. The LED device of  claim 1 , wherein the peak emission wavelength of the second phosphor layer is approximately 10 nm longer than the peak emission wavelength of the LED die. 
     
     
       3. The LED device of  claim 1 , wherein the peak emission wavelength of the second phosphor layer is approximately 10 nm to 20 nm shorter than a peak emission wavelength of the first phosphor layer. 
     
     
       4. The LED device of  claim 1 , further comprising:
 a lens surrounding the LED die, the first phosphor layer, and the second phosphor layer. 
 
     
     
       5. The LED device of  claim 1 , wherein the first phosphor layer comprises Y 3 (Al,Ga) 5 O 12 , Lu 3 (Al,Ga) 5 O 12 , SCASN, and CASN in silicone. 
     
     
       6. The LED device of  claim 5 , wherein a mass ratio SCASN to CASN is approximately 20:80. 
     
     
       7. The LED device of  claim 5 , wherein a ratio of Lu 3 (Al,Ga) 5 O 12  to SCASN and CASN is approximately 8.47. 
     
     
       8. The LED device of  claim 1 , further comprising:
 a reflective coating formed on sides of the LED die, sides of the first phosphor layer, and sides of the second phosphor layer. 
 
     
     
       9. The LED device of  claim 8 , wherein the reflective coating comprises TiO 2  in silicone. 
     
     
       10. The LED device of  claim 1 , wherein the peak emission wavelength of the LED die is approximately 440 nanometers. 
     
     
       11. The LED device of  claim 1 , wherein the peak emission wavelength of the second phosphor is approximately 20 nm to 40 nm longer than the peak emission wavelength of the LED die. 
     
     
       12. The LED device of  claim 5 , wherein a ratio of Y 3 (Al,Ga) 5 O 12  and Lu 3 (Al,Ga) 5 O 12  to SCASN and CASN is greater than 5 and less than 10. 
     
     
       13. The LED device of  claim 1 , wherein the peak emission wavelength of the second phosphor layer is approximately 460 nanometers.